1. Field of the Invention
The present invention relates to a document original size detecting device and, particularly, to a device which detects the size of a document original in an electrophotographic copying machine.
2. Description of the Related Art
A document original size detecting device of the prior art generally includes an openable document original cover which covers a document original placed on a transparent document platen provided on the top of a copying machine main body, a plurality of sensors each including a light emitting element and a light receiving element and disposed below the document platen as respectively corresponding to different sizes of document originals to be placed on the document platen, light path establishing means which establishes a light path for guiding a light beam emitted from the light emitting element through the document platen to the corresponding light receiving element by reflection with the document original cover being opened at an angle within a predetermined angular range, driving means which drives each adjacent pair of sensors in a time staggered manner, and size determining means which determines a document original size on the basis of whether or not the light beam is received on the light receiving element of each of the sensors driven in the time staggered manner (see, for example, Japanese Examined Patent Publication No. HEI5(1993)-14260).
However, if the document original has a missing portion such as a punch hole, there is a possibility that the light beam from the light emitting element passes through the missing portion to reach the light receiving element. As a result, the document original size detecting device of the prior art suffers from erroneous detection of the document original size.